A broad spectrum of materials is known at present to be based upon thermostable heterocyclic polymers.
However, only finished polymers are employed for making such materials. Initial monomers cannot be used immediately for making the above materials because the process of their transformation into polymers is accompanied either by evolution of by-products (such as H.sub.2 O, CO.sub.2, NH.sub.3) which considerably deteriorate the characteristics of the material, or by formation of structures that feature a prolonged thermooxidative stability at low temperatures not over 200.degree. to 250.degree. C. That is why use is made, for making high thermostable materials featuring best characteristics, of finished polymers which are produced by the processes of synthesis, isolation and purification, whereas the material (such as molding material) is produced by polymer processing. The presence of additional steps (synthesis, isolation and purification of the resultant polymer) substantially sophisticates production of the material, adds to the cost thereof, and requires more production areas. At the same time the stages of synthesis, isolation and purification of polymers can be obviated through the application of such starting reagents the reaction of which is not accompanied by evolution of any by-products and yields polymers featuring high thermal and thermooxidative stability.
In such case the polymer production process may be carried out concurrently with the polymer material manufacturing process. The reagents possessing the abovesaid characteristics are such as bis-orthoaminonitriles and bis-orthohydroxynitriles which in reacting with polyfunctional isocyanates form thermostable polymers of the heterocyclic structure, said reaction of bis-orthoaminonitriles or bis-orthohydroxynitriles with polyfunctional isocyanates being run at 130.degree. to 300.degree. C. within 1 to 24 hours. With a view to producing homogeneous mixtures based upon crystalline reagents featuring high melting points, it is recommended to carry out short-time heating of the reagents in the presence of a solvent, such as toluene, xylene, methylethylketone, acetone, tetrahydrofuran, ethyleneglycol dimethyl hydrine, chloroform, followed by extraction of the solvent by drying the mixture at a temperature up to 130.degree. C. The resultant homogeneous mixtures can be used as, for example, adhesives. The solution, containing bis-orthoaminonitrile or bis-orthohydroxynitrile, polyfunctional isocyanate and a solvent, can also be used for impregnating glass-, carbon- or polyamide-fiber cloth, followed by evaporation of the solvent. Various additives may be added to the mixtures based on said reagents, such as antioxidants, pigments, dyes, other polymers, resins), as well as other reagents capable of reacting with bis-orthoaminonitriles, bis-orthohydroxynitriles and polyisocyanates (diamines, diols, dithiols, isothiocyanates).
However, as tests have demonstrated, polymers resulting from said reagents feature a relatively low thermal stability and therefore are capable of long-term service at temperatures not exceeding 250.degree. to 270.degree. C.